The present invention relates generally to a catheter or cannula for infusion of oxygenated blood or other fluids into a patient for cardiopulmonary support and cerebral protection. More particularly, it relates to an arterial perfusion catheter with a deployable embolic filter for protecting a patient from adverse effects due to emboli that are dislodged during cardiopulmonary bypass.
Over the past decades tremendous advances have been made in the area of heart surgery, including such life saving surgical procedures as coronary artery bypass grafting (CABG) and cardiac valve repair or replacement surgery. Cardiopulmonary bypass (CPB) is an important enabling technology that has helped to make these advances possible. Recently, however, there has been a growing awareness within the medical community and among the patient population of the potential sequelae or adverse affects of heart surgery and of cardiopulmonary bypass. Chief among these concerns is the potential for stroke or neurologic deficit associated with heart surgery and with cardiopulmonary bypass. One of the likely causes of stroke and of neurologic deficit is the release of emboli into the blood stream during heart surgery. Potential embolic materials include atherosclerotic plaques or calcific plaques from within the ascending aorta or cardiac valves and thrombus or clots from within the chambers of the heart. These potential emboli may be dislodged during surgical manipulation of the heart and the ascending aorta or due to high velocity jetting (sometimes called the xe2x80x9csandblasting effectxe2x80x9d) from the aortic perfusion cannula. Air that enters the heart chambers or the blood stream during surgery through open incisions or through the aortic perfusion cannula is another source of potential emboli. Emboli that lodge in the brain may cause a stroke or other neurologic deficit. Clinical studies have shown a correlation between the number and size of emboli passing through the carotid arteries and the frequency and severity of neurologic damage. At least one study has found that frank strokes seem to be associated with macroemboli larger than approximately 100 micrometers in size, whereas more subtle neurologic deficits seem to be associated with multiple microemboli smaller than approximately 100 micrometers in size. In order to improve the outcome of cardiac surgery and to avoid adverse neurological effects it would be very beneficial to eliminate or reduce the potential of such cerebral embolic events.
Several medical journal articles have been published relating to cerebral embolization and adverse cerebral outcomes associated with cardiac surgery, e.g.: Determination or Size of Aortic Emboli and Embolic Load During Coronary Artery Bypass Grafting; Barbut et al.; Ann Thorac Surg 1997;63;1262-7; Aortic Atheromatosis and Risks of Cerebral Embolization; Barbut et al.; J Card and Vasc Anesth, Vol 10, No 1, 1996: pp 24; Aortic Atheroma is Related to Outcome but not Numbers of Emboli During Coronary Bypass; Barbut et al.; Ann Thorac Surg 1997;64;454-9; Adverse Cerebral Outcomes After Coronary Artery Bypass Surgery; Roach et al.; New England J of Med, Vol 335, No 25, 1996: pp 1857-1863; Signs of Brain Cell Injury During Open Heart Operations: Past and Present; Aberg; Ann Thorac Surg 1995;59;1312-5; The Role of CPB Management in Neurobehavioral Outcomes After Cardiac Surgery; Murkin; Ann Thorac Surg 1995;59;1308-11; Risk Factors for Cerebral Injury and Cardiac Surgery; Mills; Ann Thorac Surg 1995;59;1296-9; Brain Microemboli Associated with Cardiopulmonary Bypass: A Histologic and Magnetic Resonance Imaging Study; Moody et al.; Ann Thorac Surg 1995;59;1304-7; CNS Dysfunction After Cardiac Surgery: Defining the Problem; Murkin; Ann Thorac Surg 1995;59;1287+Statement of Consensus on Assessment of Neurobehavioral Outcomes After Cardiac Surgery; Murkin et al.; Ann Thorac Surg 1995;59;1289-95; Heart-Brain Interactions: Neurocardiology Comes of Age; Sherman et al.; Mayo Clin Proc 62:1158-1160, 1987; Cerebral Hemodynamics After Low-Flow Versus No-Flow Procedures; van der Linden; Ann Thorac Surg 1995;59;1321-5; Predictors of Cognitive Decline After Cardiac Operation; Newman et al.; Ann Thorac Surg 1995;59;1326-30; Cardiopulmonary Bypass: Perioperative Cerebral Blood Flow and Postoperative Cognitive Deficit; Venn et al.; Ann Thorac Surg 1995;59;1331-5; Long-Term Neurologic Outcome After Cardiac Operation; Sotaniemi; Ann Thorac Surg 1995;59;1336-9; and Macroemboli and Microemboli During Cardiopulmonary Bypass; Blauth; Ann Thorac Surg 1995;59;1300-3.
The patent literature includes several references relating to vascular filter devices for reducing or eliminating the potential of embolization. These and all other patents and patent applications referred to herein are hereby incorporated herein by reference in their entirety.
The following U.S. patents relate to vena cava filters: U.S. Pat. Nos. 5,549,626, 5,415,630, 5,152,777, 5,375,612, 4,793,348, 4,817,600, 4,969,891, 5,059,205, 5,324,304, 5,108,418, 4,494,531. Vena cava filters are devices that are implanted into a patient""s inferior vena cava for capturing thromboemboli and preventing them from entering the right heart and migrating into the pulmonary arteries. These are generally designed for permanent implantation and are only intended to capture relatively large thrombi, typically those over a centimeter in diameter, that could cause a major pulmonary embolism. As such, these are unsuitable for temporary deployment within a patient""s aorta or for capturing macroemboli or microemboli associated with adverse neurological outcomes. Vena cava filters are also not adapted for simultaneously providing arterial blood perfusion in connection with cardiopulmonary bypass.
The following U.S. patents relate to vascular filter devices: U.S. Pat. Nos. 5,496,277, 5,108,419, 4,723,549, 3,996,938. These filter devices are not of a size suitable for deployment within a patient""s aorta, nor would they provide sufficient filter surface area to allow aortic blood flow at normal physiologic flow rates without an unacceptably high pressure drop across the filter. Furthermore, these filter devices are not adapted for simultaneously providing arterial blood perfusion in connection with cardiopulmonary bypass devices.
The following U.S. patents relate to aortic filters or aortic filters associated with atherectomy devices: U.S. Pat. Nos. 5,662,671, 5,769,816. The following international patent applications relate to aortic filters or aortic filters associated with atherectomy devices: WO 97/17100, WO 97/42879, WO 98/02084. The following international patent application relates to a carotid artery filter: WO 98/24377. This family of U.S. and international patents includes considerable discussion on the mathematical relationship between blood flow rate, pressure drop, filter pore size and filter area and concludes that, for use in the aorta, it is desirable for the filter mesh to have a surface area of 3-10 in2, more preferably 4-9 in2, 5-8 in2 or 6-8 in2, and most preferably 7-8 in2. While these patents state that this characteristic is desirable, none of the filter structures disclosed in the drawings and description of these patents appears capable of providing a filter surface area within these stated ranges when deployed within an average-sized human aorta. Accordingly, it would be desirable to provide a filter structure or other means that solves this technical problem by increasing the effective surface area of the filter mesh to allow blood flow at normal physiologic flow rates without an unacceptably high pressure drop.
In keeping with the foregoing discussion, the present invention takes the form of a perfusion filter catheter or cannula having an embolic filter assembly mounted on an elongated tubular catheter shaft. The elongated tubular catheter shaft is adapted for introduction into a patient""s ascending aorta either by a peripheral arterial approach or by a direct aortic puncture. A fine filter mesh for capturing macroemboli and/or microemboli is mounted on the embolic filter assembly. The embolic filter assembly has an undeployed state in which the filter is compressed or wrapped tightly around the catheter shaft and a deployed state in which the embolic filter assembly expands to the size of the aortic lumen and seals against the inner wall of the aorta. The embolic filter assembly can be passively or actively deployable. Various mechanisms are disclosed for both passive and active deployment of the embolic filter assembly. Optionally, an outer tube may cover the embolic filter assembly when it is in the undeployed state. Radiopaque markers and/or sonoreflective markers, may be located on the catheter and/or the embolic filter assembly. Preferably, a perfusion lumen extends through the elongated tubular catheter shaft to one or more perfusion ports upstream of the embolic filter assembly. Oxygenated blood is perfused through the perfusion lumen and any embolic materials that might be dislodged are captured in the deployed embolic filter assembly.
In order to provide a sufficient flow rate of oxygenated blood for support of all critical organ systems through the filter without excessive pressure drop, it is preferred that the surface area of the filter mesh be greater than twice the cross-sectional area of the aortic lumen, more preferably three, four, five or six times greater than luminal cross section of the aorta. Preferably, the embolic filter assembly is also configured to hold at least a majority of the filter mesh away from the aortic wall when deployed to maximize the effective filter surface area. Several possible configurations are described for the embolic filter assembly that meet these parameters. The embolic filter assembly configurations described include an elongated cone, a frustum of a cone, a trumpet-shape, a modified trumpet-shape, and helically, circumferentially and longitudinally convoluted shapes. Further configurations are described having standoff members for centering the embolic filter assembly within the aorta and for holding at least a majority of the filter mesh away from the aortic walls when deployed.
Embodiments are also described that combine the perfusion filter catheter with an aortic occlusion device, which may be a toroidal balloon, an expandable balloon or a selectively deployable external catheter flow control valve. The combined device allows percutaneous transluminal administration of cardiopulmonary bypass and cardioplegic arrest with protection from undesirable embolic events. An embodiment of the perfusion filter catheter is described having an aortic transillumination system for locating and monitoring the position and the deployment state of the catheter and the embolic filter assembly without fluoroscopy.
In use, the perfusion filter catheter is introduced into the patient""s aorta with the embolic filter assembly in a collapsed state either by a peripheral arterial approach or by a direct aortic puncture. The embolic filter assembly is advanced across the aortic arch and into the ascending aorta. When the embolic filter assembly is positioned in the ascending aorta between the aortic valve and the brachiocephalic artery, the embolic filter assembly is either actively or passively deployed. The position of the catheter and the deployment state of the embolic filter assembly may be monitored using fluoroscopy, ultrasound, transesophageal echography (TEE) or aortic transillumination. Once the embolic filter assembly is deployed, oxygenated blood may be infused into the aorta through the perfusion lumen. Any potential emboli are captured by the embolic filter assembly and prevented from entering the neurovasculature or other branches downstream. After use, the embolic filter assembly is returned to the collapsed position and the catheter is withdrawn from the patient.